This application makes reference to, incorporates the same herein, and claims all benefits accruing under 35 U.S.C. xc2xa7119 from my application SUB-PICTURE ENCODING APPARATUS AND METHOD THEREOF filed with the Korean Industrial Property Office on May 29, 1998 and there duly assigned Ser. No. 19793/1998.
1. Field of the Invention
The present invention relates to a sub-picture encoding method and apparatus used in a rewritable optical disc, and more particularly, to an apparatus and method for encoding a closed caption into a sub-picture.
2. Description of the Related Art
In general, a closed caption is included in television programs, and the captions of the television programs are transmitted via the 21st line of 525 lines adopted by the National Television System Committee (NTSC) standard. That is, because 16 bits of data per field are transmitted according to the National Television System Committee (NTSC) standard, a maximum of 480 bits of closed-caption data are transmitted per second.
In a data structure for transmission of closed captions adopted in the United States (US) television broadcasting system, a closed caption consists of various control codes and caption texts. Such a closed caption is transmitted in the order of a Preamble Control Code, a Caption Text, a Mid-Caption Control Code, a Caption Text and an End-of-Caption Control Code. In detail, the Preamble Control Code contains display position and display color codes and is transmitted two times for reliable transmission. The Caption Text includes caption text data to be displayed. Also, in the United States (US), the caption text data utilizes a 7-bit USA Standard Code for Information Interchange (US ASCII) and a parity bit for error correction. The Mid-Caption Control Code is for changing the display color or shape of the caption data. The End-of-Caption Control Code indicates the end of one caption of data.
However, a television system or a video playback system exemplary of contemporary practice in the art requires an extra closed-caption dedicated decoder in order to display the closed caption data. That is, even though a television system or video playback system exemplary of contemporary practice in the art can record a video signal including closed-caption data, the closed-caption data cannot be reproduced without a closed-caption decoder.
It is an object of the present invention to provide a sub-picture encoding apparatus and method for encoding closed captions wherein a sub-picture is used in a rewritable recording medium such that closed-captions can be reproduced without an extra closed-caption decoder.
According to the present invention, there is provided an apparatus for encoding closed-caption caption data of a television signal into sub-picture data used in a rewritable recording medium, including: a caption decoder for decoding the caption signal in the television signal; and a sub-picture encoder for coding the closed-caption data decoded by the caption decoder into the sub-picture data defined for the rewritable recording medium according to a predetermined format.
Also, according to the present invention, there is provided a method for encoding closed-caption data of a television signal into sub-picture data used in a rewritable recording medium, including the steps of: (a) if a signal indicating the start of the closed caption is detected from the input television (TV) signal, setting the point in time at which the signal is detected as the ending time of display of a previously coded sub-picture data unit, and decoding text data and display information of the closed caption; (b) if a signal indicating the ending of the closed caption is detected, coding the decoded text data of the closed caption into a format defined for the rewritable recoding medium, and setting display parameters of the sub-picture from the decoded display information; and (c) if the step (b) is terminated, setting the point in time at which the setting of parameters of the step (b) is completed as the starting time of display of the current coded sub-picture unit.